1. Field of the Invention
The present invention relates, generally, to zoom lenses, and in particular embodiments, to an optionally rotatable compound zoom lens with a minimal number of moving lens groups that provides a wide focal length range and a wide field of view and is small in size to fit in consumer products such as cellular telephones and other products with compact lenses.
2. Description of Related Art
Notably lacking in the prior art are zoom lenses having a zoom ratio greater than about four combined with a maximum field of view at the short focal length position of 85 degrees or more. Although such zoom lenses are known in the field of broadcast zoom lenses, these are typically large, complex and expensive designs. Examples can be found in U.S. Pat. No. 5,745,300, and in Japanese Patents 62-153,913, 08-136,808, 09-015,501, 09-033,812 and 11-030,749.
A more compact, wide-range, wide-angle zoom can be found in U.S. Pat. No. 6,038,084, although the performance of the examples is poor despite significant complexity.
What is desired is a compact and relatively simple zoom lens with both a wide zoom range and wide field angle that can be economically produced in high volume. Such a zoom lens would have wide-ranging application in digital still and video cameras, cell phones, Personal Digital Assistants (PDAs), and the like.
Recently, a novel compound zoom system was described in related U.S. Patent Application Publication No. 20040021953. This system comprises a zoom kernel that forms an intermediate image, followed by a zoom relay that re-images the intermediate image to a final image plane. The zoom ratio of the lens system as a whole is equal to the zoom ratio of the kernel multiplied by the zoom ratio of the relay. Such a design approach has a number of potential advantages over conventional zoom lens designs, including large zoom range, wide field of view, high image quality, and flexibility in arranging fold mirrors or prisms. However, the zoom system does not provide for a compact wide-range wide-angle zoom lens that is suitable for mass-market applications.
More recently, a wide angle compound zoom system was described in related U.S. patent application Ser. No. 11/071,125, filed on Mar. 2, 2005. This system comprises four independently moving groups to achieve a zoom ratio of about 8.6 together with a field of view of 90 degrees at the short focal length position. The system is sufficiently compact to be used in a cell phone, PDA, or compact digital camera.
However, with the size of personal electronics ever decreasing, there is still a need for an even more compact and relatively simple zoom lens with both a wide zoom range and wide field angle that can be economically produced in high volume. Such a zoom lens would have broad application in digital still and video cameras, cell phones, PDAs, and the like.